The instant disclosure relates to deflectable and steerable elongate devices, such as medical catheters. In particular, the instant disclosure relates to catheters having segments with anisotropic deflecting or bending stiffness that reduce or eliminate unintended out-of-plane movement of the catheter.
Deflectable and steerable elongate devices such as catheters are used for an ever-growing number of medical, industrial, and manufacturing procedures. For example, catheters are used for diagnostic, therapeutic, and ablative procedures. During these procedures, a catheter is typically inserted into a vessel near the surface of the body and is guided to a specific location within the body for examination, diagnosis, and treatment. A catheter typically carries one or more energy emitting elements (e.g., electrodes, hyperthermic ablation elements, cryogenic elements, etc.), which may be used for tissue ablation, diagnosis, or the like. Some catheters perform only passive or diagnostic functions such as sensing the electrical waveforms of a beating heart.
Catheters are often inserted into an artery or vein in the leg, neck, or arm of a patient and guided, sometimes with the aid of a guide wire or introducer, through the vessels until a distal end of the catheter reaches a desired location in the heart. Guidance of a catheter to a specific location in the body can be performed using feel, medical imaging (e.g., fluoroscopy), electrophysiological guidance (e.g., impedance-based and/or magnetic-based localization), computer generated maps/models, and/or various combinations of the above. In any case, it may be necessary to deflect or steer the distal end of the catheter to facilitate movement of the catheter through a body cavity (e.g., vessel) and/or to position the distal end of the catheter relative to an internal structure of interest.
In this regard, guidable catheters and/or introducers typically include a selectively deflectable segment near their distal tip. For instance, an ablation catheter may include a distal end portion (e.g., insertion portion) having an ablation electrode and a relatively soft and flexible distal deflectable segment that is disposed between the electrode and a relatively more rigid (e.g., metallic wire-braided.) catheter shaft that extends to a proximal actuator. Pull wires may extend from a pull mechanism in the proximal actuator and attach to a pull ring positioned between the deflectable segment and the electrode, Upon manipulation of the actuator, the pull wires can generate a pull force that imposes a bending moment on the flexible deflectable segment. This can lead to the deflection of the distal end of the catheter, which allows the distal end to be routed to and/or positioned relative to the desired internal locations.
One or more highly flexible polymer materials are typically used to construct a single or multi-segment deflectable body of the catheter. The catheter shaft proximally adjacent to the deflectable segment(s) typically consists of relatively rigid polymer materials. To improve the deflection planarity (i.e., in-plane deflection), prior catheters have incorporated various selectively deflectable segments or catheter bodies having anisotropic bending stiffness into deflectable segments or bodies of the catheters. Other catheters have used a “center strut” bonded to the deflecting portion to assist with maintaining catheter rigidity. See, e.g., U.S. patent application publication No. 2010/0063441, which is hereby incorporated by reference as though fully set forth herein.
Difficulties with the aforementioned catheters include failing to systematically and synergistically consider axial curvatures, deflection easiness, deflection in-planarity, and elastic recovery after deflection. Deflection planarity and ease of deflection are highly desirable properties or features for a deflectable catheter.